The character Leona (who found the Fountain of Youth beneath Gallagher Elementary) is named for the Spanish explorer Juan Ponce de León, who is famous for his legendary search for the Fountain of Youth.
Possible references to the Harry Potter franchise: The plot, featuring protagonists going on an adventure to save a girl from a secret underground portion of their school accessed via a sink in the girl's bathroom, could be considered a reference to Harry Potter and the Chamber of Secrets (2002). The portion of the episode set in the ancient school's gymnasium could be a reference to the life-sized chess board in Harry Potter and the Sorcerer's Stone (2001).